... kha˙’nˇang cu˙’a el`a x v`a luˆo`ng trˆen e l`a y.stbcde• •• •• •3, 2 5, 3 2, 2 2, 1 2, 2 4, 34, 2 .................................................................................................... ... Φ 2 + 1 ◦ Φ3,trong d¯´oP1= {s, v 2 , v4, t},P 2 = {s, v1, v3, v 2 , v4, t},Φ1= {v1, v3, v 2 , v1},Φ 2 = {v 2 , v4, v5, v6, v 2 },Φ3= {v5, v6, v7, v5}.7.3 ... vˆa.y,F = 1 ◦ (P1) + 1 ◦ (P 2 ) + · · · + 1 ◦ (Pv) + 1 ◦ (Φ1) + 1 ◦ (Φ 2 ) + · · · + 1 ◦ (Φκ),1 82 http://www.ebook.edu.vnstbcde• •• •• •35 2 2 2 44.......................................................................................................